Knowing the primary structure of a protein is fundamental to understanding its structure and function at a molecular level. Research is presently underway here to elucidate the amino acid sequence of several proteins and this supplemental proposal is requesting funds to purchase an automatic solid phase peptide sequenator which will be used to facilitate these research programs. The proteins being investigated fall into several categories. a) A number of hormones are known to mediate their effects through c-AMP-dependent protein kinase. This enzyme can activate or inactivate a number of proteins by phosphorylating a single serine or threonine residue. Protein kinase is being purified from porcine muscle and the primary structure of both the catalytic and regulatory subunits are being elucidated in the laboratory of the principal investigator. b) In this same laboratory the amino acid sequence of dogfish M4 LDH has been elucidated and work is presently underway to elucidate the amino acid sequence of other lactate dehydrogenases which show fundamental differences in their stereospecificity allosteric control properties, and/or subunit structure. These LDH's will provide models for studying the evolution of specific regions of this molecule and should enable us to correlate specific changes in primary structure to changes in enzyme specificity and quaternary structure. c) In the laboratory of one of the co-investigators, Dr. Nathan O. Kaplan, the sequencing ofthe beta-chain of diphtheria toxin is being initiated. d) The second co-investigator, Dr. Helen Ranney, is characterizing a number of human hemoglobin variants in an attempt to correlate changes in primary structure to specific changes in the functional properties of the molecule as well as to establish the molecular basis for various hemoglobinopathies. This instrument will be used in all of the above projects and will greatly facilitate the rate at which these primary structures can be elucidated. The merit of these projects has already been established by the fact that these projects are each funded presently by National Institutes of Health research grants.